1. Field of the Invention
This invention relates to a heat storage material utilizing the latent heat of fusion of CH.sub.3 CO.sub.2 Na.multidot.3H.sub.2 O.
2. Description of the Prior Arts
Known heat storage materials utilize the sensible heat or the latent heat. A heat storage material utilizing the latent heat has a larger heat storage capacity per volume or mass than that utilizing the sensible heat, and can store a necessary amount of heat in a smaller quantity, permitting smaller size of the heat storage device. A heat storage material utilizing the latent heat can store and release heat at a constant transition temperature. A heat storage material which utilizes the latent heat of fusion of a hydrate, in particular, is known to have a larger heat storage capacity per unit volume.
CH.sub.3 CO.sub.2 Na.multidot.3H.sub.2 O is heretofore known to have a particularly larger latent heat of fusion among hydrates. However, since the melting point of CH.sub.3 CO.sub.2 Na.multidot.3H.sub.2 O is not a congruent melting point but a peritectic point, "phase separation" phenomenon proceeds in which CH.sub.3 CO.sub.2 Na deposits on the bottom of the vessel as the fusion and solidification are repeated. For this reason, the latent heat of fusion of CH.sub.3 CO.sub.2 Na.multidot.3H.sub.2 O is decreased naturally by repeated storage and release of heat. This decrease of the latent heat accompanying the phase separation has been a major problem when CH.sub.3 CO.sub.2 Na.multidot.3H.sub.2 O is used as the heat storage material.